152 research outputs found
Powerline communications systems: overview and analysis
No full textThe electric power distribution grid is a medium over which fast and reliable communication services can be provided. Power Line Communications (PLC) systems provide an alternative to wireless communications in the transmission of data within buildings and vehicles. In recent years, increased interest in PLC systems for both commercial and residence applications has resulted in the development of standards for use of the electric power grid as a communications channel conveying messages in addition to power. The types of applications range from simple inexpensive services centered around networked household appliances, where data rates are on the order of kilobits per second, to Internet access via the electrical outlet wall socket, where data rates are on the order of megabits per second. Currently, PLC systems can accommodate high- iii speed networking that includes broadband Internet access, voice over-IP, and the interconnectivity of home entertainment devices. The development of a Power Line Communications system presents a significant challenge for the communications engineer due to the unusual channel characteristics that affect high-speed signal transmission. The electric power grid is designed for, and operated at, 50/60 Hz throughout the world. Furthermore, the topology of a local electric power grid network is often very irregular resulting in significant dispersion of the transmitted message signals. This thesis presents an overview of the major features and characteristics of PLC systems, the fundamental properties of powerline channels, and an analysis of PLC system performance in the presence of realistic powerline channel conditions. The development of a powerline communication system requires detailed knowledge of the electric power grid channel properties, such as the frequency transfer function and the interference processes, in order to choose a suitable transmission method. The noise interference and channel multipath effects are the main impairments to the performance of PLC systems. This thesis presents appropriate channel models for use in the design of PLC systems. In particular, the Bit Error Rate (BER) performance of a single-carrier Binary Phase Shift Keying (BPSK) system operating over a multipath channel is analyzed and compared with the performance obtained with a multi-carrier data transmission scheme.M.S.Includes bibliographical referencesby Nishant Saga
Municipal solid waste incineration ashes: origin, composition, and reactivity in cementitious systems
No full textThis Thesis was approved for publication on 2021-06-29 at 09:56.Municipal Solid Waste (MSW) management primarily involves recycling, landfilling, and incineration for energy recovery. MSW composition data based on site-specific studies and material flow analysis indicates the presence of plastics in the municipal solid waste stream of U.S. states. Specifically, in an MSW stream solely consisting of paper, food, yard, plastic, metal, and glass material glasses, the plastic fraction ranges between 20 and 25 % in the discarded waste stream of U.S. states. Unfortunately, technological barriers limit the recycling of plastic fractions. In absence of recycling, the non-recyclable plastics and contaminated MSW are landfilled, resulting in environmental emissions. However, given the advancements in air pollution control devices, incineration for energy recovery can be a better alternative to landfilling. Data collected shows that presently incineration capacity of U.S. states is inadequate to process the MSW generated. Further expansion of incineration (waste-to-energy) facilities is unlikely considering the costs associated with the landfilling of incineration residues, i.e., MSWI Ashes. Research investigations had indicated that MSWI ashes can be compositionally comparable to coal fly ash, blast furnace slag, and clay. Thus, the MSWI ashes may find applications as a supplementary cementitious material. Successful utilization of MSWI ashes as supplementary cementitious material can reduce the expenses associated with the landfilling of MSWI ashes and improve the commercial viability of the waste-to-energy (WTE) industry.
Despite being compositionally similar to other supplementary cementitious materials, the MSWI ashes are largely unutilized as supplementary cementitious material. This is because the performance of a cementitious system in the presence of MSWI ashes is not well investigated. Thus, in this thesis, the behaviour of cementitious systems containing MSWI ashes was investigated. Specifically, the hydration behaviour of ordinary Portland cement blended with 8 distinct and diverse MSWI ashes was studied. The findings indicate that incorporating these MSWI ashes can either accelerate or retard cement hydration depending upon their composition. Specifically, Cu, Fe, Al, Ti, Si, K, Zn, and Sr from the MSWI ash matrix appear to retard cement hydration, while Pb, Br, S, Ca, and Cl appear to accelerate cement hydration. Based on these results, a performance predicting parameter – Incineration Ash Coefficient (IAC) – was introduced that correlates with the 7-day compressive strength of mortars incorporating MSWI ashes reasonably well (R2=0.79). This new parameter, based on fundamental chemical and physical characteristics of ashes, can aid in the selection and employment of MSWI ashes as supplementary cementitious materials.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2023-08-01The student, Vikram Kumar, accepted the attached license on 2021-06-25 at 10:27.The student, Vikram Kumar, submitted this Thesis for approval on 2021-06-25 at 11:05.DSpace SAF Submission Ingestion Package generated from Vireo submission #16721 on 2022-01-12 at 13:03:42Made available in DSpace on 2022-01-12T22:51:41Z (GMT). No. of bitstreams: 2
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Intersubband polaritonic metasurfaces for flat nonlinear optics
No full textMuch attention has been drawn in recent years towards the creation of two-dimensional equivalents of traditionally three-dimensional optical elements. The reduction in dimensionality offers advantages such as a smaller spatial footprint, reduced manufacturing and operating complexity, and access to more exotic optical functionalities than can be achieved in a traditional bulk optics approach. Metasurface-based flat optical components, comprised of arrays of subwavelength-spaced scatterers, have emerged as a promising candidate for the realization of this vision, but have been largely constrained to the domain of linear interactions of light with matter. Nonlinear effects are intrinsically weak in bulk materials, and even more so across subwavelength volumes, meaning realization of practical and efficient nonlinear optical metasurfaces has generally been out of reach. In this thesis, a series of metasurface designs are proposed and experimentally verified to exhibit record setting nonlinearities across deeply subwavelength volumes. The metasurfaces are comprised of metallic nanoantennas patterned onto multiple-quantum well structures possessing tailored intersubband electronic resonances. We term the ensemble structure an Intersubband Polaritonic Metasurface (IPM), owing to the nature of the coupling of the electromagnetic antenna mode with the electronic intersubband transition. Suitable design of the antenna geometry allows one to access and enhance the giant intrinsic nonlinearity of intersubband transitions, which are subject to polarization-selection rules that typically inhibit their operation configuration. Further, due to their subwavelength thickness, IPMs are not constrained to the typical phase-matching considerations of bulk nonlinear optics. In the first part of this study, we investigate IPMs for efficient second-harmonic generation. A novel architecture consisting of etched nanoantenna volumes is proposed and experimentally demonstrated to exhibit a record setting second-order nonlinearity in the mid-infrared spectral range. Using this design, we experimentally demonstrate a means to control the phase of the generated nonlinear signal via the Pancharatnam-Berry geometric phase approach. We then present and demonstrate a simplified fabrication procedure for the creation of efficient IPMs, forgoing the rather cumbersome wafer-bonding and substrate removal process inherent to earlier designs. Finally, we propose and verify a metasurface design exhibiting an ultrafast third-order nonlinearityElectrical and Computer Engineerin
Disinformation overload : ‘truthing it’ in algorithmic networks
No full textFake news has been all the news lately. The anxiety around fake news is a symptom of a growing instability in our capacity to tell, discern, filter, share, and amplify that which we believe to be true, in the algorithmic state of information networks. Fake news is not so much about searching for the truth, as it is about figuring out the first principles through which claims of truth can be made. Beginning with the idea of information overload as our new default, this talk looks at the way in which our first order principles of truth claiming are being challenged, manipulated, and reformed by the algorithmic practices of computational networks. Drawing from digital cultures, software studies, network theory, feminist technologies, and humanist critique, this talk unpacks the transitions that engineer the new conditions of ‘faking it’ and potentials for possible hacks.
近期「假新聞」往往成為「新聞」。我們對假新聞的焦慮，正表示了我們對數位資訊世 界中所相信的「真相」感到愈來愈無力去訴說、分辨、過濾、分享和闡明。假新聞並不 關於「求真」，而是要弄清楚宣稱真相的根本原理。這次講座由我們都認知的「資訊超 荷」做起點，去探討真相宣稱的根本原理如何已被電腦化網絡的演算法所挑戰、主導及 改革。這次講座會從數碼文化、軟體研究、網絡理論、女性主義科技、人本批判的角度 出發，探討如何從「假裝」中尋找出路。
Speaker
Prof. Nishant Shah is a feminist, humanist, technologist working in digital cultures. He is the Vice-President Research at the ArtEZ University of the Arts, The Netherlands. where he is invested in thinking through infrastructure of art, culture, and design for building resilient and equitable futures. He is a Senior Research Fellow in Media Cultures of Computer Simulation at Leuphana University, Germany, working through questions of simulation and the new technosocial subjectivities that emerge thereof. He was the co-founder of the Centre for Internet & Society India, where the work on technological ordering he initiated continues to inform his current preoccupations. He is a knowledge partner with the development agency Hivos, The Netherlands, analyzing new practices of collective action. His work remains at the interlocked edges of the body, identity, digital technologies, policy, and activism. His current interest is in thinking through questions of ethics and inclusion within Artificial Intelligence systems. Prof. Nishant Shah’s profile website: https://nishantshah.online
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Denise Tse-Shang Tang is an interdisciplinary ethnographer who began her career by studying the relationship between lesbian sexualities and social spaces in Chinese societies. She is the author of Conditional Spaces: Hong Kong Lesbian Desires and Everyday Life (Hong Kong University Press, 2011). She co-edited (with Alistair Fraser and Maggy Lee) “Crime, Media, Culture: Asia-style,” special issue of Crime, Media, Culture, and is one of the editors (with Stevi Jackson and Olivia Khoo) for the Palgrave MacMillan book series Gender, Sexualities and Culture in Asia
Optimization of cellular concrete for impact-resistant infrastructure
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Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemCellular concrete is an intentionally low strength, low density (300-1400 kg/m3) construction material with a cellular structure that has proven useful in the development of impact-resistant infrastructure such as explosion barriers in mines and military engineering projects as well as aircraft arresting systems. Like other cellular solids, energy absorbed during crushing is defined by the load-deformation response curve, in which a plateau is indicative of crushing behavior at a near-constant load. At the microstructural level, the energy absorbed from crushing is a combination of elastic buckling, plastic yield, and brittle fracture of the cellular microstructure. Therefore, the optimization of this cellular structure (e.g., bubble size and distribution) is paramount to the overall performance of these systems. Currently, however, the design of this material is largely an iterative process that can have adverse effects on the quality, reliability, and cost of impact-resistant infrastructure.
The goal of this research is to inform better design of impact-resistant infrastructure by identifying cellular concrete microstructures which lead to optimal energy absorption in low-velocity impact events (e.g., automotive crashes). Specifically, this work explores a gap in the existing literature regarding the development of cellular concrete microstructures capable of effective energy absorption. Commercial foaming agents with varying interfacial properties were used to create cellular concrete samples at densities ranging from 20-60 % of the cementitious base. X-ray computed tomography investigations were implemented to quantify the three-dimensional nature of the resulting cellular concrete microstructures. Additionally, investigations of the hydration kinetics and early age properties of the cementitious base were completed to study the interaction between the amphiphilic surfactant molecules, which are the surface-active components of the commercial foaming agents, and cement grains. The effects of the observed microstructural variations on the mechanical properties of cellular concrete were investigated under quasi-static loading and low-velocity impact events.
The experimental investigations show that independent of density, the cellular concrete microstructure can be controlled by foaming agents and that these microstructural variations influence the energy absorption capability of cellular concrete at densities below 1000 kg/m3. This builds on existing cellular concrete literature, which shows the mechanical properties are primarily controlled through the relative density of the material (i.e., foam content). Given the range of cellular concrete microstructures identified in this study, a new micromechanical model was developed to link the microscopic properties of cellular concrete with constitutive behaviors. Preliminary results are promising, demonstrating that it is possible to capture the effects of microstructural variation through numerical modeling efforts.
Although this study focuses on cellular concrete, the findings are broadly applicable to other cellular solids that behave in a similar manner. Thus, this work has the potential to aid in the design of cellular ceramics, metals, and plastics for a variety of applications, including lightweight scaffolding, cushioning, filtration, insulation, and other crushable energy absorbers.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2022-12-01The student, Jamie Clark, accepted the attached license on 2020-11-20 at 11:08.The student, Jamie Clark, submitted this Dissertation for approval on 2020-11-20 at 11:14.This Dissertation was approved for publication on 2020-11-23 at 08:15.DSpace SAF Submission Ingestion Package generated from Vireo submission #15918 on 2021-03-04 at 16:32:07Made available in DSpace on 2021-03-05T21:45:33Z (GMT). No. of bitstreams: 2
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Reperfusion Therapy for Acute Ischemic Stroke
No full textThis eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contac
Dynamic Modelling and State Estimation of a High Speed Racing Drone
No full textAutonomous drone racing has taken a turn for the better in recent years. Drones are becoming faster and implementing better state-of-the-art control techniques to overcome different challenges. With advancements in the fields of computer vision, machine learning, and artificial intelligence, the final goal of autonomous drones is to be quicker than human-piloted racing drones. Increasing the speed of autonomous drones increases the risks associated with flying them. Time-optimal control algorithms have been identified as a method of implementingaggressive maneuvers to fly drones at high speeds throughout the course of the race. These methods require precise state-estimates. This research work identifies a model for the rate controller. The work also includes an implementation of a state estimation model with drag compensation, also merging a pre-existing refined thrust model with Coriolis effects. With the idea of developing a state estimation model for a racing drone, the model is improved toinclude flight envelopes involving motor saturations.Aerospace Engineerin
Physico-chemical characterization of choline chloride based deep eutectic solvents used in CO<sub>2</sub> absorption and electrochemical conversion process
No full textIncreasing CO2 concentration in the atmosphere has caused significant concern, paving the way to research and develop technologies like capture carbon and storage (CCS) and carbon capture and utilization (CCU). This thesis focuses on extracting CO2 from Chimney stacks and regenerating the solvent using electrochemistry. The main aim of this thesis is to identify a solvent that is capable of being used as a good CO2 capture medium and at the same time as an electrolyte for CO2 reduction.Deep eutectic solvents (DES) have been gaining much attention due to their desirable properties such as biodegradability, low vapour pressure, and high tunability for the required purpose. Research has shown promising results in the application of DES in the field of CO2 capture at a lower price with more eco-friendly solvent. Choline chloride is the most widely used quaternary amine salt which has all the desirable properties; when combined with a CO2 philic hydrogen bond donor group such as amines, a novel solvent could be formed. The low/negligible vapour pressure of DES makes it suitable for CO2 absorption in industrial applications. Based on the literature, three different solvents were selected, Choline chloride and Ethylene glycol (ChCl:EG), Choline chloride and Monoethanolamine (ChCl:MEA) and Choline chloride with Aminomethyl propanol (ChCl:AMP).Various experiments were conducted on different molar ratios of selected solvents to determine the physico-chemical properties. Viscosity was measured as it affects the CO2 absorption capacity due to limiting the mass transfer and has a significant impact on ion mobility resulting in high ohmic drops and reduced efficiency of the electrochemical extraction process. Conductivity was also measured as having higher conductivity will reduce the ohmic drop and improve the CO2 removal process; conductivity is inversely related to viscosity. Effect of varying temperature, water and CO2 loading was observed on these physical properties.Based on the experiments conducted, it was found that ChCl:EG solutions have the highest conductivity among the pure solvents, with some of the lowest viscosities. In the case of ChCl:MEA, the viscosity reduced with the increase in temperature and increased drastically on the absorption of CO2. This is because of the formation of carbamates as confirmed by FTIR. ChCl:AMP is a unique solvent as absorption of CO2 results in the formation of a bicarbonate precipitate, as shown in FTIR.Addition of EG to ChCl:MEA solution improves the performance of the DES significantly. At similar CO2 loading, the viscosity of ChCl:EG:MEA (1:4:3) is almost 63.88% less and the electrical conductivity 134.45 % more than ChCl:MEA(1:6)Mechanical Engineerin
Model Predictive Control for Automated Driving and Collision Avoidance: Design of an integrated NMPC with simultaneous lateral and longitudinal control via steering and braking
No full textThe automotive sector has seen a rapid transition towards autonomous driving with an aim to achieve SAE Level 5 vehicle. The incessant drive for innovation has resulted in modern passenger cars equipped with plethora of control technologies such as ABS, VSC, AFS via EPS assist etc. all working respectively in various critical and non-critical scenarios to ensure safe and smooth driving at all times. These efforts have reduced the number of road accidents significantly over the past years, yet it was observed that the number of rear-end crashes have not decreased but has rather maintained its proportion which is about 1/3rd of all road accidents. An evasive maneuver, a limit-handling situation, involves quick steering or braking action to avoid colliding with the vehicle in-front (thus avoiding a rear-end crash). A normal human driver is not trained to drive and control car in such demanding and high stress inducing task. This warrants the needs of an autonomous controller design that can itself take over the control of car and perform the maneuver successfully. The aim of this research was to verify this statement by designing a novel control scheme that can steer and brake simultaneously ensuring collision avoidance and passenger safety at all times. The controller designed uses the state-of-the-art Model Predictive Control (MPC) scheme such that best possible performance can be extracted even in critical driving scenarios. Variety of simulations were performed to successfully conclude that MPC worked well and is robust in design as well
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